Slashing and burning of tropical rainforests releases hundreds of thousands of tonnes of carbon into the atmosphere every year. Furthermore the burned forest is no longer there to absorb more carbon. The bare soil left behind readily erodes. This soil erosion often leads to a reduction in the quality of drinking water as sediment is washed into the rivers and streams. In coastal areas, such as the North coast of Honduras, the sediment runs eventually on to the coral reef and smothers it. When the forest is no longer there to absorb the rain and release it slowly floods occur.
Rainforests contain extremely biodiverse ecosystems, containing about half of all animal species. They are being steadily destroyed and are not easily replaced.
Large rainforests also help to maintain rainfall both locally and in wide areas beyond their borders.
If we are to save the remaining tropical forests, an estimated 250 million slash and burn farmers have to be given an alternative means of feeding their families. Inga alley cropping can be this alternative for many. By settling farmers onto sustainable plots it can stop the endless cycle of slashing and burning, both reducing carbon emissions and leaving the forests to absorb more carbon.
Inga alley cropping normally requires no use of agricultural chemicals or pesticides. Agricultural chemicals often destroy the natural organisms of the soil that keep a soil healthy and fertile, poison wildlife, poison people and the runoff creates dead zones in the seas off coasts.
(The original research on Inga alley cropping recommended rock phosphate but we have not found that to be necessary. If one does have to use rock phosphate to start the system on very severely degraded land then it is still far removed from the use of many fertilizers, herbicides ash pesticides.)
Inga alley cropping has been shown to yield up to 15 times the harvests when used on previously degraded land. This is in comparison with plots planted beside the Inga plots. This means that large tracts of land can be reused for farming, or for reforestation.
Deforested areas are soon invaded by weeds, which create barren, treeless wastelands. For much of the wildlife used to the cover of tropical forests this closes their migration routes. The extent of their habitats is thus severely reduced, trapping them in rapidly dwindling patches of forest. Not only can Inga farming reduce this deforestation but Inga trees can be used in reforestation of these wild life corridors.
Not only is the cycle of destruction stopped, but when previously used plots of grass or scrub are converted to Inga alley cropping this means more carbon being absorbed per hectare per year. The red soil so common in the tropics turns black, indicating carbon sequestration. We are currently working to further quantify this benefit. Pruned wood can be burned, a sustainable source of cooking fuel which replaces wood that would otherwise be taken from the rainforest, thus saving forest.
The Inga alleys can last for many years gradually absorbing increasing amounts of carbon. Furthermore land, barren after slash and burn, can be recaptured using Inga trees and replanted with new forest. This too can be a valuable carbon sink.
With land available to slash and burn rapidly disappearing or becoming increasingly infertile many farmers are being forced into poorly paid plantation work or worse into burgeoning city slums. If farmers can be settled on small plots of land, this will not only make the farmers self-sufficient but will also slow the growth of the unsustainable slums.
When farmers no longer need to move to seek new plots far away this helps to stabilize the community (or encourage the creation of a new community). Stabilizing groups of poor families in an area can lead in the longer term to the development of villages, schools and other institutions beneficial to all.